KEF LSX re­view

Macworld (USA) - - Contents - BY SCOTT WILKIN­SON

Founded in 1961, KEF is a well-known, high-end Bri­tish speaker brand with many out­stand­ing prod­ucts to its credit. These days, small wireless speak­ers are all the rage, and KEF has em­braced that mar­ket with sev­eral mod­els, in­clud­ing the new LSX. Let’s see if it’s wor­thy of KEF’S legacy.

The KEF LSX is rel­a­tively small, mea­sur­ing 9.5 x 6.1 x 7.1 inches (H x W x D), but it feels quite sub­stan­tial (weigh­ing just un­der eight pounds). To match al­most any decor, it’s avail­able in five col­ors: black, green, blue, red, and gloss white. In each case (ex­cept white), the sides, top, and bot­tom are wrapped in a color-matched fab­ric from Dan­ish tex­tile de­signer Kvadrat.

A gen­tly con­vex front baf­fle helps min­i­mize dif­frac­tion of sounds from the driver. Speak­ing of which, the driver is a Kef-de­vel­oped Uni-q coax­ial de­sign. A 0.75-inch alu­minum-dome tweeter is lo­cated at the cen­ter of a 4.5-inch mag­ne­sium/alu­minum al­loy-cone midrange/woofer. This con­fig­u­ra­tion is in­tended to make sounds from both trans­duc­ers ra­di­ate from the same point and im­prove stereo imag­ing.

The Uni-q driver is pow­ered by am­pli­fiers pro­vid­ing 70 watts for the midrange/woofer and 30W for the tweeter. KEF spec­i­fies a fre­quency range (-6 db) up to 47khz; the low end of that range de­pends on the Bass Ex­ten­sion set­ting in the KEF Con­trol app: 49-, 52-, or 55Hz. By con­trast, the fre­quency re­sponse (±3 db) is spec­i­fied up to 28khz and down to 54-, 59-, or 69Hz, de­pend­ing on the Bass Ex­ten­sion set­ting. The low end is en­hanced by a port on the back of the speaker as well as KEF’S Mu­sic In­tegrity En­gine dig­i­tal sig­nal pro­cess­ing. The max­i­mum out­put is spec’d at 102db SPL.

As a wireless speaker, the LSX ac­cepts au­dio via Blue­tooth 4.2 (with sup­port for the aptx codec), and it will re­mem­ber up to eight Blue­tooth de­vices. It will also sup­port Ap­ple Air­play 2 in a soon-to-bere­leased firmware update. In ad­di­tion, it can stream mu­sic from on­line providers Ti­dal and Spo­tify as well as lo­cal NAS drives or com­put­ers via DLNA over your home’s Wi-fi net­work (2.4- or 5GHZ, 802.11a/b/g/n).

The LSX sup­ports dig­i­tal-au­dio streams with res­o­lu­tions up to 192khz/24-bit. Eth­er­net con­nec­tions, how­ever, max out at 96/24, and wireless con­nec­tions are lim­ited to 48/24, so any­thing higher is down­sam­pled as needed.

This speaker is sold in pairs; one is called the Mas­ter and the other is called the Slave. The Mas­ter pro­vides all the con­nec­tions on its back panel, in­clud­ing a Toslink op­ti­cal dig­i­tal-au­dio in­put and a 3.5mm 2-chan­nel ana­log-au­dio in­put as well as a hard­wired eth­er­net con­nec­tor for greater band­width on your net­work. Other

con­nec­tions in­clude a USB port for au­dio on a USB stor­age de­vice and an RCA sub­woofer out­put if you want to add a sub to the system.

Nor­mally, the two speak­ers are paired wire­lessly us­ing a pro­pri­etary 2.4GHZ wireless sig­nal, but a ded­i­cated RJ45 con­nec­tor on the back of both speak­ers lets you con­nect them with an included eth­er­net ca­ble if you wish. (As with wireless stream­ing, a wireless con­nec­tion be­tween the speak­ers is lim­ited to 48/24 au­dio, while a wired con­nec­tion al­lows up to 96/24.)

Round­ing out the Mas­ter’s back panel are three but­tons that fa­cil­i­tate Blue­tooth pairing, Mas­ter/slave pairing, and re­set­ting the system. Nor­mally, those but­tons aren’t needed, since you set up the system us­ing an app on your mo­bile de­vice (more in a mo­ment).

I usu­ally do not com­ment on the AC power re­cep­ta­cle, but I will in this case. The LSX uses a 3-prong grounded power cord—which is good!—but the re­cep­ta­cle

is not IEC 320 C13, which is nearly ubiq­ui­tous, at least in the US; it’s IEC 320 C5, which you can see in the photo of the con­nec­tions. When I asked KEF about this, they replied, “The foot­print for the 320 C5 con­nec­tor is slightly smaller, and with the phys­i­cal space avail­able, that small amount of saved space was im­por­tant.” Still, I wish it was C13, which would make it much eas­ier for many own­ers to re­place a lost power cord.


Each pair of LSX speak­ers comes with a small re­mote con­trol with six but­tons: power on/off, source se­lect, volume up, volume down, mute, play/pause, skip for­ward, and skip back. It feels good to the touch with a matte-black fin­ish.

You set up the speak­ers us­ing the KEF Con­trol app, which is free for An­droid and IOS de­vices. The app guides you through the setup pro­ce­dure (which I’ll discuss shortly), and then dis­plays the main screen that lets you se­lect the source, con­trol play­back, and mute the speak­ers.

From the main screen, you can se­lect Set­tings, which pro­vide a va­ri­ety of con­trols. These in­clude con­nect­ing the two speak­ers with an eth­er­net ca­ble rather than wire­lessly, in­vert­ing the L/R speaker as­sign­ments, set­ting standby-mode time, set­ting volume in­cre­ments, ini­ti­at­ing firmware up­dates, and oth­ers.

Also from the main screen, you can se­lect the KEF Au­dio Sig­na­ture con­trols, which let you cre­ate and save pro­files based on the place­ment of the speak­ers in your room

and your in­di­vid­ual pref­er­ences. These con­trols are di­vided into two groups: Ba­sic and Expert.

The Ba­sic con­trols in­clude whether the speak­ers are on stands or on a desk, the dis­tance to the wall, the acoustic char­ac­ter­is­tic of the room (damped, mod­er­ate, or lively), the size of the room, and whether you have a sub connected. The Expert con­trols in­clude a tre­ble trim, phase cor­rec­tion, bass-ex­ten­sion set­ting, high­pass mode, sub­woofer cross­over, sub gain, and sub po­lar­ity.


I placed the KEF LSX speak­ers on top of the main speak­ers in my mas­ter bed­room, where I could try them out us­ing Blue­tooth and an op­ti­cal ca­ble from the TV. The KEF Con­trol app guided me through the setup process step by step. All went smoothly un­til I got to con­nect­ing the speak­ers to my Wi-fi net­work; the app didn’t see the speak­ers in its net­work list.

I hit “Can’t lo­cate speaker,” and the app in­formed me that the light on the Mas­ter should be blink­ing am­ber and white; it was blink­ing am­ber only. The app in­structed me to re­set the speak­ers us­ing a pa­per clip in the tiny re­set hole, af­ter which the light blinked am­ber and white. The app then found the speak­ers in the net­work list, and the rest of the process went with­out a hitch.

It’s pos­si­ble to set up the LSX speak­ers with­out Wi-fi, but that limits the system’s func­tion­al­ity and is not gen­er­ally rec­om­mended.

As I was lis­ten­ing, I played with the sound set­tings in the KEF Con­trol app. Af­ter spec­i­fy­ing that the speak­ers were on stands rather than on a desk, I set the size and acoustic char­ac­ter­is­tic of the room as well as dis­tance to the wall. The dis­tanceto-wall slider has no in­di­ca­tion of its ac­tual set­ting; it only in­di­cates the small­est and largest set­tings (<10cm and >50cm re­spec­tively). I wish it had a nu­meric in­di­ca­tor un­der the slider it­self, like some of the other slid­ers do.

The ef­fect of the Tre­ble Trim and Bass Ex­ten­sion con­trols is sub­tle; I found that I pre­ferred the de­fault set­tings. In par­tic­u­lar, the Ex­tra bass set­ting sounded a bit boomy.


I listened to a va­ri­ety of se­lec­tions from an ipad via Blue­tooth. First up was “Au­tumn in New York” from the Heath Broth­ers’ al­bum Af­ter Mid­night. The sound was beau­ti­ful; the acoustic bass was deep and throaty, the tenor sax was faith­fully ren­dered, and the pi­ano and drums were nice and clean.

An­cient Fu­ture is one of my fa­vorite world-mu­sic fu­sion groups, so I listened to “Se­mara” from the al­bum Planet Pas­sion. Mathew Mont­fort’s scal­loped-fret gui­tar was crys­tal clear, as were the eth­nic flute, cello, tablas, and an In­done­sian met­alo­phone (sort of a metal xy­lo­phone). I was es­pe­cially im­pressed with the sharp tran­sients of the tablas and met­alo­phone. “El Zaffa” from the same al­bum has gui­tar, elec­tric bass, a string sec­tion, and var­i­ous eth­nic per­cus­sion, and all were ren­dered faith­fully with su­perb de­lin­eation of the in­stru­ments.

Next up was Billy Joel’s “River of Dreams” from his al­bum of the same name. I was im­me­di­ately stunned by the ex­pan­sive imag­ing I heard. In par­tic­u­lar, the back­ground vo­cals were spread pre­cisely across the en­tire sound­stage, and Joel’s voice and pi­ano were clearly de­lin­eated along with the bass, gui­tar, and drums.

For a mostly elec­tronic sound, I turned to Loop Guru’s “White Light” from the al­bum Loop Bites Dog. The en­tire sound was rich and full, with ex­cel­lent synth bass. Like­wise, the imag­ing was quite ex­pan­sive.

Moving on to or­ches­tral mu­sic, I listened to the Fi­nal Waltz and Apotheo­sis from The Nutcracker by P.I. Tchaikovsk­y as per­formed by Valery Gergiev and the Orches­tra of the Kirov Opera. The bal­ance be­tween the dif­fer­ent in­stru­men­tal sec­tions was su­perb, and the dy­namic range from the quiet be­gin­ning of the apotheo­sis to the crash­ing con­clu­sion was art­fully ren­dered.

An­other of my fa­vorite groups is Ore­gon. “Rewind” from the al­bum Be­yond Words con­sists only of gui­tar, so­prano sax, and acoustic bass, each of which were re­pro­duced beau­ti­fully with ex­cel­lent de­lin­eation.

In ad­di­tion to Blue­tooth, I connected my Sony TV’S op­ti­cal dig­i­tal-au­dio out­put

to the KEF LSX system. Af­ter watch­ing Mir­a­cle Work­ers and The Big Bang The­ory on TBS, Law & Or­der on Sun­dance, and The Fifth El­e­ment on Syfy, it was clear that the speak­ers de­liver rich, full sound with ex­cel­lent di­a­log in­tel­li­gi­bil­ity. By com­par­i­son, the Har­man Kar­don En­chant 800 sound­bar I re­cently re­viewed sounded some­what thin with ex­ag­ger­ated sibi­lants.

Of course, in this use case, it would be best to pro­gram the TV or uni­ver­sal re­mote with the LSX volume, mute, and source­s­e­lec­tion re­mote com­mands.

Oth­er­wise, you must jug­gle at least two re­motes.


By now, it should be ob­vi­ous that I love the sound of the KEF LSX. These speak­ers are small but mighty, paint­ing a richly de­tailed, mm­mmh well-bal­anced sonic pic­ture. Even my wife, who isn’t very fussy about au­dio quality, no­ticed how good the LSX speak­ers sound—with no prompt­ing from me. Of course, you could get even bet­ter bass by adding a sub­woofer, though the LSX is cer­tainly no slouch in the bass depart­ment all by it­self, es­pe­cially con­sid­er­ing its size.

The build quality is equally im­pres­sive; these things are as solid as bricks! They are per­fect for place­ment on a desk to ac­com­pany a com­puter or a book­shelf to fill a room with beau­ti­ful mu­sic. (I would not place them within a small, en­closed book­case or right up against a wall, which would block the rear ports. Such place­ment would dra­mat­i­cally de­grade the sound.) They can even en­hance TV sound bet­ter than many sound­bars! And these speak­ers look fan­tas­tic do­ing it.

My only real com­plaint is that the LSX does not wake up from standby mode and automatica­lly switch to the ac­tive in­put when it re­ceives a sig­nal. Of less im­por­tance, the less-com­mon AC power con­nec­tor makes it a bit more dif­fi­cult to re­place a lost power cord.

Then there’s the price: $1,100 for the pair ain’t cheap! But if you can af­ford them and you need big sound from a small pack­age, the KEF LSX is hard to beat. ■

The KEF Uni-q driver con­sists of a 0.75inch alu­minum-dome tweeter lo­cated at the cen­ter of a 4.5-inch mag­ne­sium/alu­minum al­loy-cone midrange/woofer.

The KEF LSX is avail­able in an ar­ray of col­ors to match your decor. Apart from the gloss-white model, the sides of the cab­i­nets are wrapped in a color-matched fab­ric from Dan­ish tex­tile de­signer Kvadrat.

A nice com­ple­ment of con­nec­tions. No­tice the AC power re­cep­ta­cle; it’s an IEC stan­dard con­fig­u­ra­tion, but not the one I would have wished for.

The Expert set­tings let you set the bass ex­ten­sion, ex­ter­nal sub­woofer pa­ram­e­ters, and other things.

The small, sim­ple re­mote pro­vides but­tons for power on/off, source se­lec­tion, volume up and down, mute, play/pause, and skip for­ward and back.

KEF LSX wireless speak­ers de­liver prodigous amounts of high-quality au­dio for their size.

In this exploded view of the Uni-q driver, you can clearly see the com­plex­ity of its de­sign.

The KEF LSX is chock full of so­phis­ti­cated elec­tron­ics, driver com­po­nents, and brac­ing to keep the cab­i­net from vi­brat­ing.

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